One of the most iconic buildings in the New York skyline recently achieved a milestone in its quest to become one of the greenest buildings in America.

2011 marks the 80th anniversary of the Empire State Building, and instead of showing its age, the building is celebrating an achievement that makes new construction jealous.

The Empire State Building was recently awarded LEED Gold certification, making it the most well known building in the US to receive green building certification from the US Green Building Council (Reuters).

The LEED rating system is offered by the U.S. Green Building Council to help building owners and construction companies make the most environmentally friendly decisions for the buildings in which we live and work. LEED certification is available at four levels -- Certified, Silver, Gold and Platinum -- that correspond to the number of credits accrued in five green design categories: sustainable sites, water efficiency, energy and atmosphere, materials and resources and indoor environmental quality (NRDC).

In January 2011, the Empire State Building Company announced its plan to purchase over 50 million kilowatt-hours worth of renewable energy certificates annually — the equivalent of every house in New York State turning off all its lights for a week.

The Empire State Building's LEED Gold status is also the result of a $550 million renovation that included fitting each of the building's 6,514 double-hung, dual-pane windows with energy-efficient insulation. The green improvements will reduce the building's carbon emissions by an estimated 105,000 metric tons over 15 years.

Image Credit: Flickr - Ami's